The two–mass three–loop contributions [1]} read
\(\hat{\hat{h}}_3^{\rm NS} &=& P_{qq}^{(0)} \beta _{0,Q}^2\left[\frac{2}{3} \left(L_c^3 + L_b^3\right) + \frac{1}{2}\left(L_c^2 L_b +L_c L_b^2 \right)\right] - \beta _{0,Q} \hat{P}_{qq}^{(1),\rm NS} \left(L_c^2 + L_b^2\right)-\left[4 a_{qq,Q}^{(2),\rm NS} \beta _{0,Q} \right.\nonumber \\ && \left.- \frac{1}{2} \beta _{0,Q}^2 P_{qq}^{(0)} \zeta _2\right] (L_c + L_b)+ 8 \bar{a}_{qq,Q}^{(2),\rm NS} \beta _{0,Q} + \tilde{a}^{(3),\rm NS}_{qq,Q}(m_c,m_b,Q^2).\) 
